Holder and mounting means for ceramic crt cathode ring

ABSTRACT

An electron gun for a cathode-ray tube has a cathode centrally mounted in a ceramic ring. The ring has a metal holder comprising a flat plate with means extending about the periphery of the ring and forming a clamp against the other side. The cathode assembly is held in the electron gun assembly by embedding the edges of a flat plate extending from the ring into a pair of glass beads. The cathode is critically spaced from a grid comprising a flat apertured plate by having edges of the plate embedded in the same glass beads.

United States Patent Inventor Horst H. lllulnenberg Oweosboro, Ky.

Appl. No. 6398 Filed Jan. 28, 1970 Patented July 20, 1971 AssigneeKentucky Electronics Corporation Owenshoro, Ky.

HOLDER AND MOUNTING MEANS FOR CERAMIC CRT CA'I'IIODE RING 9 China, 4Drawing Figs.

US. Cl 313/82 R, 3.13/289 Int. Cl 1101] 1/94, H01 j 29/02FieldotSearchJ. 313/289, 82, 81

[56] References Cited UNITED STATES PATENTS 2,195,914 4/1940 Baier3l3/82 2,462,921 3/1949 Taylor... 313/289 X 3,239,708 3/1966 Johnson 3 l3/82 Primary ExaminerRoy Lake Assistant Examiner-V. LafranchiAttorney-Laurence R. Brown ABSTRACT: An electron gun for a cathode-raytube has a cathode centrally mounted in a ceramic ring. The ring has ametal holder comprising a flat plate with means extending about theperiphery of the ring and forming a clamp against the other side. Thecathode assembly is held in the electron gun assembly by embedding theedges of a flat plate extending from the ring into a pair of glassbeads. The cathode is critically spaced from a grid comprising a flatapertured plate by having edges of the plate embedded in the same glassbeads.

PATENTEU JUL20 I97! v INVENTOR HORST H. BLUMENBERG B'Y W62. 6W

ATTORNEY HOLDER AND MOUNTING MEANS FOR CERAMIC CRT CATIIODE RING ingstructures is expensive because the cup must be deep drawn and theinterfitting parts must be formed to very close tolerances.

Other mounting techniques have been proposed to reduce cost whileretaining precise dimensional stability such as that in the copendingapplication of Horst H. Blumenberg and John Midkiff and entitled CathodeMount in Single Gun Indicia Tube," sn 843,3I6 filed July 22, 1969, andassigned to the assignee of this application. Therein the cathodeextends from and is conductively connected to a flat metallic plateembedded at opposite ends in the two glass beads which hold the variouselectron gun electrodes in position.

It is well recognized however that a critical relationship of cathodeand grid parts is necessary in many electron guns to maintain thenecessary operability characteristics with the elevated cathodetemperatures that tend to cause attendant changes of position because ofthermal expansion and changes in emission because of generation of heatpockets. Thus careful control of thermal dissipation paths and relativepositioning and shaping of parts is required with special metals forcontrolled expansion with heat or controlled conductivity of heat.

'It is therefore an object of this invention to provide an operablestructure affording acceptable performance under critical CRT conditionswhich is simple and inexpensive in structure and is operable withoutsignificant problems of variable emission, changing position of parts orrequisite careful control of thermal conductivity.

It has been found in accordance with the invention therefore that asimple inexpensive holding and mounting arrangement for the cathodeassembly in a CRT electron gun array can be provided with littlecriticality or variation in performance even when subjected to verystringent spacing and performance specifications necessary in miniaturetubes. Such a mount has asa feature a cathode held in a ceramic ringwhich has a holding means thereabout holding the ring adjacent aflatapertured plate which extends from the peripheral edge of the ring andis embedded in two opposed glass beads. The ring is held in a clampedposition on the flat plate by a metallic structure clamped to the ringon the side opposite from the plate. This holder structure iselectrically insulated from a first grid, which preferably comprises aflat apertured plate held in a pair of opposed glass beads by embeddededges of the grid plate. I

A more detailed description of the electron gun structure afforded bythis invention is set forth together with further features, objectivesand advantages of the invention in the following specification whereinreference is made to the embodiments set forth in the accompanyingdrawing, in which:

FIG. 1 is a perspective view of a cathode, disc and holder assemblyafforded by this invention,

FIG. 2 is a plan view of a holder plate assembly,

FIG. 3 is an elevation view, partly in section, of a cathoderay tubeelectrode assembly embodying the invention, and

FIG. 4 is a plan view assembly of a further embodiment of acathode-disc-holder assembly afforded by the invention.

Now with reference to FIG. I a cathode assembly for a cathode ray tube(CRT) electron gun array is shown. This array comprises a ceramic ringhaving a centrally located cylindrical cup shaped cathode 11 with aplanar emitting surface 12 (FIG. 3) disposed in a plane generallyparallel to one passed through the body of theceramic ring 10. Thecathode 11 passes through an aperture in the center of ceramic disc 10.The cathode assembly is provided with a flat plate mounting means 14which extends away from the ceramic disc 10 so that opposite ends 13,-13may be embedded in opposed glass beads 17, 18. For the purpose ofproviding a firm support to hold the cathode in a fixed known positionin the electron gun, the ends may have notches 19, 20 therein.

A holder assembly 15 extends about the outer peripheral surface ofceramic disc 10 from one side to terminate in clamping means contiguousto the disc 10 on the opposite side. In the embodiment shown in FIGS. 1and 2, a separate apertured flat plate 21 has a set of integral tabs 16extended therefrom which may be bent at regions 22 and 23 to extendabout the outer periphery of the ring at region 24 and serve to clampthe ring in place with the portion 25 disposed on the upper surface 26of the ceramic ring. With this particular embodiment the holder assembly15 about the ceramic ring 10 can be prefitted on the ring and thenwelded on a separate flat mounting plate 14. Deep drawn or moreexpensive cuplike retainers are not necessary with this structure, andtherefore it is preferred, although the holder assembly 15 could bemanufactured in other ways such as by forming a cup to hold the disc 10on one side and rolling over the lip as clamping means on the otherside, or by having a pair of half-cups on either side of the disc weldedtogether.

With this arrangement of a separate flat mounting plate 14 and discholder assembly 15, the two pieces may be relatively positioned andwelded together at a proper position for disposing the emitting surface12 of the cathode along the axis of the CRT electron gun, to therebygive some degree of freedom of selection of the cathode 10 positionrelative to the mounting plate 14 position.

If the latter degree of freedom is not necessary a singlepiece structuremay be used as shown in FIG. 4 wherein the mounting plate 44 itselfserves also as the holder structure for the ceramic disc 10 by means oftabs 16 that may be formed in and bent away from the planar surface ofthe mounting plate to achieve the relationship on the disc periphery andupper surface set forth in FIG. 1.

Since the cathode assembly must be critically spaced and oriented in theelectron gun with respect to the first grid, its relationship in the CRTassembly pictured in FIG. 3 is important. The cathode surface 12 musthave a precise spacing relative to the first grid 30, which is a flatapertured plate embedded at its end portions in the beads I7, 18. Theuse of the flat plates 14 and 30 minimizes any chance for twisting anddistortion of spacing or tube characteristics because of thermalreaction on bent or stressed areas in cuplike or other bent or shapedmountings and for this reason the flat plate mounting structuresafforded by this invention are not only inexpensive to manufacture butprovide improved operating characteristics.

In addition this structural arrangement permits simple inexpensivemounting pieces to be designed in a way that can provide any necessarydegree of thermal heat conductivity through the ceramic disc 10 from thecathode l1, and prevents the heat pocket" characteristics existing whena cuplike grid envelops the cathode assembly. Furthermore, the firstgrid 30 is not extended in the vicinity of the filament leads 31 (as acup grid might be) where it may pick up noise or interference, and thusalso presents a low interelectrode gridcathode capacitance whichcontributes to superior high frequency signal characteristics. Thecathode mounting plate 14 may be left electrically floating or may beconnected to ground as a suitable potential level to gather strayelectrons, etc.

With this structure the first grid 30 and the cathode may be held in asimple jig and embedded in the beads l7, 18 along with the second grid38, the focus electrode 32, anode 33, deflection plates 34, 35, 36 andthe snubber spring mounting structure 37 in a precise interelectrodespacing and orientation relationship. This assembled relationship withthe cathode mount structure afforded herein permits a miniature tube tobe constructed with electrostatic deflection electrodes for meetingexacting dimensional and operational specifications. A typical sizerelationship of the tube illustrated is 3 inches in overall length of anenvelope (not shown) having three-fourths of an inch diameter unflaredcylindrical configuration terminating in a flat phosphor screen at theviewing end.

What I claim is:

1. An assembly for a cathode-ray tube electron gun array comprising incombination,

a ring of insulating material,

a cathode mounted centrally in said ring and presenting a planaremitting surface in a plane parallel to a plane passed through saidring,

a holder about said ring comprising an apertured plate located on oneside of said ring having clamping means extended about the outerperipheral surface of said ring and disposed contiguously on theopposite side of said ring,

and means extending from said plate for mounting said cathode in a fixedposition in said electron gun array.

2. The assembly defined in claim 1 wherein said cathode comprises aclosed cylindrical cup extending through said ring and said aperturedplate.

3. The assembly defined in claim 1 wherein said integral clamping meanscomprise a plurality of separated tabs extend ing from said aperturedplate and formed about said ring.

4. The assembly defined by claim 1 including, a first grid electrode,and insulating means spacing said grid from the planar surface of saidcathode to electrically isolate said grid from said apertured plate.

5. The assembly defined by claim 4 wherein the insulating means spacingthe grid comprises a pair of glass beads.

6. The assembly defined by claim 5 wherein said grid consists of a flatplate having a centrally locatedaperture with edges of said plateembedded in said glass heads.

7. The assembly defined by claim 5 wherein said means extending fromsaid plate for mounting said cathode comprises plate like meansextending in substantially a given plane with edges embedded in saidglass beads.

8. The assembly defined by claim 1 wherein the holder about said ringhas said clamping means integrally extending from a plate contiguouslycontacting said one side of said ring.

9. The asscmbly defined by claim 8 wherein the clamping means consistsof a plurality of discrete tabs located about the periphery of saidring.

1. An assembly for a cathode-ray tube electron gun array comprising incombination, a ring of insulating material, a cathode mounted centrallyin said ring and presenting a planar emitting surface in a planeparallel to a plane passed through said ring, a holder about said ringcomprising an apertured plate located on one side of said ring havingclamping means extended about the outer peripheral surface of said ringand disposed contiguously on the opposite side of said ring, and meansextending from said plate for mounting said cathode in a fixed positionin said electron gun array.
 2. The assembly defined in claim 1 whereinsaid cathode comprises a closed cylindrical cup extending through saidring and said apertured plate.
 3. The assembly defined in claim 1wherein said integral clamping means comprise a plurality of separatedtabs extending from said apertured plate and formed about said ring. 4.The assembly defined by claim 1 including, a first grid electrode, andinsulating means spacing said grid from the planar surface of saidcathode to electrically isolate said grid from said apertured plate. 5.The assembly defined by claim 4 wherein the insulating means spacing thegrid comprises a pair of glass beads.
 6. The assembly defined by claim 5wherein said grid consists of a flat plate having a centrally locatedaperture with edges of said plate embedded in said glass beads.
 7. Theassembly defined by claim 5 wherein said means extending from said platefor mounting said cathode comprises plate like means extending insubstantially a given plane with edges embedded in said glass beads. 8.The assembly defined by claim 1 wherein the holder about said ring hassaid clamping means integrally extending from a plate contiguouslycontacting said one side of said ring.
 9. The assembly defined by claim8 wherein the clamping means consists of a plurality of discrete tabslocated about the periphery of said ring.